The subject matter of the present invention relates generally to electrical attenuators and switching therefor, and in particular to a precision remotely-switched attenuator which may provide variable attenuation ratios as well as fixed ratios.
In electronic instrumentation, attenuator stages and amplifier stages are common building blocks in designing the signal processing path. Historically, attenuators combined mechanically actuated switches or relays with passive electrical circuit elements. These electro-mechanical attenuators offered good DC and high-frequency performance as long as they were properly maintained; however, they are fixed in attenuation ratio, slow in switching, relatively expensive and bulky, and often unreliable as parts became worn, pitted, or dirty.
Programmable step attenuators have been developed in which mechanical switches have been replaced with electronic switches, such as bipolar or field-effect transistors Examples of this type of attenuator are shown in U.S. Pat. No. 4,121,183 to Desmond L. Murphy and U.S. Pat. No. 4,523,161 to Frank Miles, both of which are assigned to the assignee of the present invention.
Trends in semiconductor and hybrid-circuit technology have resulted in programmable electronic instruments which are smaller and lighter in weight, consume less power, and provide higher performance operation with greater reliability. Often these programmable instruments require remotely switched, electronically activated, fast-acting, variable attenuators.